How do I remember the electrode products?

Cathode is reduction and attracts cations; anode is oxidation and attracts anions. List the ions first, then rank them.

Why divide by 96 500?

One mole of electrons carries 96 500 coulombs, so charge divided by that constant gives moles of electrons.

S5 Chemistry Electrolysis, Paper 1: discharge order and Faraday calculations

2026-11-02

Tutor Prep Guide · Primary English

Ten graded items on the products at each electrode, charge and mole of electrons, deposited mass and gas volume.

Focus　Decide which species discharges first, then use Q equals I t, divide by 96 500 for moles of electrons and scale by the electron number.

01　Paper details (check answers afterwards)

Item	Detail
Questions	10
Suggested time	25
Difficulty mix	Foundation 4 · Intermediate 3 · Challenge 2 · Error redo 1
Chapter	Chapter: S5 Chemistry: Electrolysis
Level	Four basic, three advanced, two challenge and one error-repair item

02　Questions (10 items)

FoundationWhat forms at the cathode when molten sodium chloride is electrolysed?
FoundationWhat forms at the anode when molten sodium chloride is electrolysed?
FoundationWhich gas is released at the cathode during electrolysis of concentrated sodium chloride solution?
FoundationWhen electroplating, which electrode should the object be connected to?
IntermediateA current of 2.0 A flows for 1 800 s. Find the charge passed.
IntermediateUsing the same 3 600 C, how much copper is deposited at the cathode from copper sulphate solution, with Cu as 63.5 and F as 96 500?
IntermediateCopper electrodes are used to electrolyse copper sulphate solution. How does the blue colour change over time?
ChallengeA current of 0.50 A flows for 1 930 s through silver nitrate solution. Find the mass of silver deposited, with Ag as 107.9.
ChallengeMolten sodium chloride is electrolysed at 2.0 A for 30 minutes. Find the volume of chlorine at room conditions, with molar volume 24 dm^3 mol^-1.
Error redoA student says the anode is the negative electrode in electrolysis. Give the correct statement.

03　Answers and one-line notes

#	Answer	One-line note
1	Sodium metal	Sodium ions are attracted to the cathode and gain electrons to form sodium metal.
2	Chlorine gas	Chloride ions lose electrons at the anode and pair up into chlorine molecules.
3	Hydrogen	Hydrogen ions from water are reduced more readily than sodium ions, so hydrogen is released.
4	The cathode, the negative electrode	The metal ions must gain electrons at the cathode, so the object is the cathode and the plating metal the anode.
5	3 600 C	Charge is current times time, so 2.0 amperes for 1 800 seconds gives 3 600 coulombs.
6	About 1.18 g	The charge gives about 0.0373 mol of electrons, half that much copper, and about 1.18 grams.
7	It stays much the same	Copper dissolves at the anode as fast as it is deposited at the cathode, so the blue colour stays much the same.
8	About 1.08 g	965 coulombs is 0.010 mol of electrons, and silver is monovalent, so about 1.08 grams forms.
9	About 0.448 dm^3	3 600 coulombs gives 0.0187 mol of chlorine after the two-electron step, about 0.448 cubic decimetres.
10	In electrolysis the anode is positive and the cathode negative, the opposite of a cell.	In an electrolytic cell the anode is the positive electrode and the cathode the negative one, the reverse of a cell.

04　What to do after marking

After marking, redo only the wrong items and write down which step went wrong (formula, unit, or misread number).
Repeat the same item two days later; move to the next paper only when both attempts are correct.
Parents only need the answer and note columns; there is no need to explain every item.

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